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Seagrasses worldwide provide key habitats for fish assemblages. Biogeographical disparities in ocean climate conditions and seasonal regimes are well-known drivers of the spatial and temporal variation in seagrass structure, with potential effects on associated fish assemblages. Whether taxonomically disparate fish assemblages support a similar range of ecological functions remains poorly tested in seagrass ecosystems. In this study, we examined variation in the abundance, diversity (from a taxonomic and functional perspective), and assemblage structure of fish community inhabiting nine meadows of the seagrass Cymodocea nodosa across three regions in the Mediterranean (Mallorca and Alicante) and the adjacent Atlantic (Gran Canaria), and identified which attributes typifying the structure of meadows, and large-scale variability in ocean climate, contributed most to explaining such ecological variation. Despite a similar total number of species between Mallorca and Gran Canaria, the latter region had more taxonomically and functionally diverse fish assemblages relative to the western Mediterranean regions, which translated into differences in multivariate assemblage structure. While variation in the abundance of the most conspicuous fish species was largely explained by variation in seagrass structural descriptors, most variation in diversity was accounted for by a descriptor of ocean climate (mean seasonal SST), operating at regional scales. Variation in fish assemblage structure was, to a lesser extent, also explained by local variability in seagrass structure. Beyond climatic drivers, our results suggest that lower temporal variability in the canopy structure of C. nodosa meadows in Gran Canaria provides a more consistent source of food and protection for associated fish assemblages, which likely enhances the more abundant and diverse fish assemblages there. [ABSTRACT FROM AUTHOR]

Seagrass meadows are crucial habitats on nearshore areas, which are exposed to human disturbances that frequently cause seagrass loss. Although demographic and mapping data have been widely used in long‐term monitoring programmes, the integration of multi‐locus genotype data through time remains rare.The present work links, for the first time, landscape, demographic, and genetic data for a seagrass, so as to explore long‐term responses to persistent human impacts. The temporal patterns in meadow area, shoot density, and clonal and genetic diversity of three Cymodocea nodosa meadows were compared: in one meadow directly affected by the construction of an industrial port and in two control areas. The hypothesis tested was that seagrass deterioration and subsequent habitat loss at the affected meadow would be associated with a reduction of seagrass clonal and genetic diversity.The results show significant reductions in both meadow area (from approx. 21 to 1.5 ha) and shoot density (from approx. 1,800 to 400 shoots per m2) at the impacted meadow, with concurrently reduced clonal and allelic richness (by approx. 22%), as well as heterozygosity (HLmean, approx. 21%; Hobs, approx. 12%). These descriptors, however, remained stable, or even increased, in the controls.Importantly for seagrass management, multi‐disciplinary analysis made it possible to link slower, large‐scale, landscape and genetic degradation processes with faster demographic deterioration on an intermediate meadow scale. Multi‐locus genotype data were also crucial for revealing long‐term degradation processes at the genetic level, which is undetectable by traditional monitoring techniques.In summary, this holistic approach provides a valuable framework for long‐term seagrass monitoring programmes to detect cumulative signals of seagrass meadow degradation across a range of scales. [ABSTRACT FROM AUTHOR]

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Human impacts accelerate the intensity and frequency of perturbations on ecosystems; approaches that integrate responses across organization levels are, however, lacking, particularly in the ocean. We experimentally simulated the frequency of fertilization ('chronic' versus 'pulse' events) in orthogonal combinations of two intensities ('large' versus 'moderate' fertilization) to determine physiological and biological responses by the seagrass Cymodocea nodosa and associated flora (epiphytes and green seaweeds, specifically Caulerpa prolifera), as well as functional changes (community primary and secondary productivity) at the ecosystem level. We predicted that the absence of recovery time from chronic perturbation would more severely affect responses at population and ecosystem levels relative to discrete events (pulses). Nutrient enrichment increased the biomass of C. prolifera irrespective of its frequency, whereas seagrass biomass and shoot density particularly decreased under a chronic scenario. These demographic responses were connected with varying photo-physiological performance of both C. nodosa and C. prolifera. Fertilization, regardless of its intensity and frequency, decreased the maximum photosynthetic rate of C. nodosa, concomitant with increased pigments, particularly under chronic fertilization, and decreased photoprotective (phenols) compounds. In contrast, fertilization boosted the maximum photochemical yield of C. prolifera, in addition to an increase in pigments and photoprotective compounds. Community primary and secondary productivity, however, did not vary under fertilization of varying intensity and frequency. In summary, fertilization precipitated population-level changes in physiological and biological attributes of vegetation. However, fertilization effects did not entirely cascade into ecosystem-level processes, that is, ecosystem productivity, which suggests a functional compensation (that is, increased algal performance to offset losses of seagrass production) during the initial stages of fertilization. [ABSTRACT FROM AUTHOR]

Seagrass habitats are relevant for numerous nearshore fish species, particularly as nursery grounds. Seagrass meadows are often interspersed with other habitats, what can alter the distribution and abundance of seagrass ichthyofauna. This research aimed to determine whether there is a change in the abundance and biomass of the parrotfish, Sparisoma cretense, in seagrass meadows ( Cymodocea nodosa) with varying proximity from rocky reefs, specifically seagrass interiors (>200 m away from reefs) vs. seagrass adjacent to reefs (<10 m away). Sampling was undertaken using a seine net and underwater visual census through an entire annual cycle. Adults were predominantly observed in seagrass adjacent to reefs, which seem to be restricted to incursions of large-sized parrotfish from adjacent reefs. Juvenile abundance did not significantly differ between seagrass interiors and seagrass adjacent to reefs; however, juvenile biomass was greater in seagrass meadows adjacent to reefs compared to those far away from reefs. This pattern was consistent through times for both sampling techniques. These results suggest a transition of juvenile parrotfish from seagrass interiors to seagrass near reefs, so juveniles are located in the vicinity of their adult habitat, i.e. rocky reefs. [ABSTRACT FROM AUTHOR]

Abstract: The shoot density, leaf length and biomass of the seagrass Cymodocea nodosa (Ucria) Ascherson were found to severely decline in the last 17 years in the oceanic island of Gran Canaria (central Eastern Atlantic). Five seagrass meadows were sampled in summer and winter of 1994–1995 and in winter and summer 2011. The decrease in C. nodosa correlated with a 3-fold increase in the biomass of the green rhizophytic algae Caulerpa prolifera (Forsskål) J.V. Lamoroux over the same time period, although this increase varied notably among meadows. We also documented a negative correlation between the biomass of C. nodosa and C. prolifera at the island-scale, sampling 16 meadows in 2011. Experimental evidence demonstrated that C. prolifera can cause significant negative impacts on C. nodosa: plots with total (100%) removals of C. prolifera had ca. 2.5 more shoots and 3.5 times more biomass of C. nodosa, after 8 months, compared to plots with 50% removals and untouched control plots. Interference by C. prolifera appears to partially explain the decay in the abundance of C. nodosa populations in Gran Canaria. This study, however, did not identify potential underlying processes and/or environmental alterations that may have facilitated the disappearance of C. nodosa. [Copyright &y& Elsevier]

The recognition of marine vegetation in the fossil record brings useful information about past environmental conditions. The paleo-biogeography of seagrasses is largely unknown, since fossilized materials are rare. In this study, we report the existence of fossil deposits of a seagrass species, Halodule cf., at Gran Canaria Island (28° N, northeastern Atlantic). The identification was confirmed by the presence of fossilized plagiotrophic rhizomes and fruits/seeds in sedimentary deposits from the early Pliocene. This seagrass fossilized material is the first from the West African coasts. The presence of this seagrass in the Canary Islands is linked with warm-water conditions during the Pliocene. [ABSTRACT FROM AUTHOR]

Amphipods are one of the dominant epifaunal groups in seagrass meadows. However, our understanding of the biogeographical patterns in the distribution of these small crustaceans is limited. In this study, we investigated such patterns and the potential drivers in twelve Cymodocea nodosa meadows within four distinctive biogeographical areas across 2000 Km and 13° of latitude in two ocean basins (Mediterranean Sea and Atlantic Ocean). We found that species abundances in the assemblage of seagrass-associated amphipods differed among areas following a pattern largely explained by seagrass leaf area and epiphyte biomass, while the variation pattern in species presence/absence was determined by seagrass density and epiphyte biomass. Seagrass leaf area was also the most important determinant of greater amphipod total density and species richness, while amphipod density also increased with algal cover. Overall, our results evidenced that biogeographical patterns of variation in amphipod assemblages are mainly influenced by components of the habitat structure, which covary with environmental conditions, finding that structurally more complex meadows harboring higher abundance and richness of amphipods associated. • We examine drivers of variation in seagrass-associated amphipods across 2000 Km in two ocean basins. • Structurally more complex meadows host greater density and richness of amphipods. • Seagrass leaf area drives higher amphipod total density and species richness, and the former also increase with algal cover. • Seagrass density and epiphyte biomass drive variation in species identity, while leaf area and epiphyte biomass explain abundances. • Attributes of habitat structural complexity selected as predictors covary with environmental factors. [ABSTRACT FROM AUTHOR]

Abstract: Marine vegetated habitats, e.g. seagrass meadows, deliver essential functions and services to coastal ecosystems and human welfare. Impacts induced by humans, however, have facilitated the replacement of seagrasses by alternative vegetation, e.g. green rhizophytic seaweeds. The implications of habitat shifts for ecosystem attributes and processes and the services they deliver remain poorly known. In this study, we compared ecosystem structure and function between Cymodocea nodosa seagrass meadows and bottoms dominated by Caulerpa prolifera, a green, native, rhizophytic seaweed, through 5 ecological proxies: (i) primary production (via community metabolism), (ii) composition and abundance of epifauna (a proxy for provision of habitat for epifauna), composition and abundance of (iii) small-sized (juvenile) and (iv) large-sized (adult) fishes (proxies for provision of habitat for fishes), and (v) sediment retention (a proxy for sediment stabilization). Four of these proxies were greater in C. nodosa seagrass meadows than in C. prolifera beds: gross primary productivity (∼1.4 times), the total abundance, species density and biomass of small-sized fishes (∼2.1, 1.3 and 1.3 times, respectively), the total abundance and species density of large-sized fishes (∼3.6 and 1.5 times, respectively), and sediment stabilization (∼1.4 times). In contrast, the total abundance and species density of epifauna was larger (∼3.1 and 1.7 times, respectively) in C. prolifera than in C. nodosa seagrass beds. These results suggest that ecosystem structure and function may differ if seagrasses are replaced by green rhizophytic seaweeds. Importantly, ecosystem functions may not be appropriate surrogates for one another. As a result, assessments of ecosystem services associated with ecosystem functions cannot be based on exclusively one service that is expected to benefit other services. [Copyright &y& Elsevier]

Abstract: Seagrass meadows are deteriorating worldwide. However, numerous declines are still unreported, which avoid accurate evaluations of seagrass global trends. This is particularly relevant for the western African coast and nearby oceanic archipelagos in the eastern Atlantic. The seagrass Cymodocea nodosa is an ‘ecological engineer’ on shallow soft bottoms of the Canary Islands. A comparative decadal study was conducted in 21 C. nodosa seagrass meadows at Gran Canaria Island to compare the structure (shoot density, leaf length and cover) between 2003 and 2012. Overall, 11 meadows exhibited a severe regression, while 10 remained relatively stable. During this period, natural influences (sea surface temperature, Chlorophyll-a concentration and PAR light, as well as the number of storm episodes detaching seagrasses) had a low predictive power on temporal patterns in seagrass structure. In contrast, proximity from a range of human-mediated influences (e.g. the number of outfalls and ports) seem to be related to the loss of seagrass; the rate of seagrass erosion between 2003 and 2012 was significantly predicted by the number of human-mediated impacts around each meadow. This result highlights promoting management actions to conserve meadows of C. nodosa at the study region through efficient management of local impacts. [Copyright &y& Elsevier]

Seagrasses are key habitat-forming species of coastal areas. While previous research has demonstrated considerable small-scale variation in seagrass abundance and structure, studies teasing apart local from large-scale variation are scarce. We determined how different biogeographic scenarios, under varying environmental and genetic variation, explained variation in the abundance and structure (morphology and biomass allocation), epiphytes and sexual reproduction intensity of the seagrass Cymodocea nodosa. Regional and local-scale variation, including their temporal variability, contributed to differentially explain variation in seagrass attributes. Structural, in particular morphological, attributes of the seagrass leaf canopy, most evidenced regional seasonal variation. Allocation to belowground tissues was, however, mainly driven by local-scale variation. High seed densities were observed in meadows of large genetic diversity, indicative of sexual success, which likely resulted from the different evolutionary histories undergone by the seagrass at each region. Our results highlight that phenotypic plasticity to local and regional environments need to be considered to better manage and preserve seagrass meadows. • Seagrasses are key habitat-forming species worldwide. • Different biogeographic scenarios explain variation in seagrass structure. • Attributes of seagrass leaf canopy evidenced regional seasonal variation. • Belowground allocation was driven by local-scale variation. • High seed densities occurred in meadows of high genetic diversity. [ABSTRACT FROM AUTHOR]